Antepartum risk factors for newborn encephalopathy: the Western Australiancase-control study

Objective To ascertain antepartum predictors of newborn encephalopathy in t erm infants. Design Population based, unmatched case-control study. Setting Metropolitan area of Western Australia,June 1993 to September 1995. Subjects All 164 term infants with moderate or severe newborn encephalopath y; 400 randomly selected controls. Main outcome measures Adjusted odds ratio estimates. Results The birth prevalence of moderate or severe newborn encephalopathy w as 3.8/1000 term live births. The neonatal fatality was 9.1%. The risk of n ewborn encephalopathy increased with increasing maternal age and decreased with increasing parity. There was an increased risk associated with having a mother who was unemployed (odds ratio 3.60), an unskilled manual worker ( 3.84), or a housewife (2.48). Other risk factors from before conception wer e not having private health insurance (3.46), a family history of seizures (2.55), a family history of neurological disease (2.73), and infertility tr eatment (4.43). Risk factors during pregnancy were maternal thyroid disease (9.7), severe pre-eclampsia (6.30), moderate or severe bleeding (3.57), a clinically diagnosed viral illness (2.97), not having drunk alcohol (2.91); and placenta described at delivery as abnormal (2.07). Factors related to the baby were birth weight adjusted for gestational age between the third a nd ninth centile (4.37) or below the third centile (38.23). The risk relati on with gestational age was J shaped with 38 and 39 weeks having the lowest risk. Conclusions The causes of newborn encephalopathy are heterogeneous and many of the causal pathways start before birth.